JP2986438B2 - Duty change circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duty changing circuit, and more particularly to a duty changing circuit which can easily change the duty of a pulse by using a Schmitt circuit in an image display device such as a monitor.

[0002]

2. Description of the Related Art Generally, in an image display device such as a monitor, when a high-voltage fluctuation occurs due to a change in horizontal and vertical frequencies for synchronizing a video signal output from a computer body, a part or the whole of a monitor screen is displayed. Is distorted. In order to correct such a screen distortion, it is necessary to design a circuit so that high-voltage fluctuation due to a change in frequency is reduced.

As a conventional general duty changing circuit for correcting a phenomenon in which a part or the whole of a screen is distorted, a change in a secondary load on a transformer in a power supply circuit of a monitor is sensed, and a change in the sensed load is detected. There is a horizontal duty change circuit that adjusts the duty based on the duty, and a duty change circuit that adjusts the duty by sensing the change with a horizontal output transistor through which a large current flows by utilizing the fact that the current changes greatly due to a load change.

According to a horizontal duty change circuit that senses a change in the load on the secondary side of a transformer and adjusts the duty according to the change in the detected load, the beam current generated in the secondary winding of the FBT (flyback transformer) increases. As the horizontal image size increases, while the beam current decreases, the horizontal image size becomes constant. In such a horizontal duty changing circuit, when the voltage applied to the FBT changes, the rate of high voltage change of the FBT becomes very large, and the voltage applied to the screen also changes. The lower the voltage applied to the screen and the voltage induced from the FBT, the darker the screen becomes. In particular, when the voltage applied to the contrast resistor changes, the brightness of the back raster also changes drastically. That is, a phenomenon occurs in which the brightness of the screen is greatly changed by a video signal having a low voltage level, and the image quality is deteriorated. In addition, F
The method of adjusting the duty by sensing the secondary current of the BT and feeding back the sensed signal has a problem that the response speed is delayed.

A conventional technique for solving such a problem will be described with reference to FIG. Computer body 1
The data processed in 00 is converted into a video signal by the video card 110. In order to display this video signal on the monitor screen, the video card 110 outputs a horizontal synchronization signal H-SYNC and a vertical synchronization signal V-SYNC. The horizontal synchronization signal H output from the video card 110
-SYNC and the vertical synchronization signal V-SYNC are
Microcomputer (microcomputer) built in 00
The microcomputer 210 starts executing the microcomputer control program stored in advance and
0 is the horizontal synchronizing signal H- according to the microcomputer control program.
SYNC, a vertical synchronization signal V-SYNC, and a horizontal size signal H-SIZE are output.

The horizontal synchronizing signal H-SYNC and the vertical synchronizing signal V-SYNC output from the microcomputer 210 are input to a horizontal and vertical oscillation signal processor 280, and the horizontal and vertical oscillation signal processor 280 uses a reference oscillation signal. To compensate the band and correct the linearity. The horizontal oscillation signal processed by the horizontal and vertical oscillation signal processor 280 is input to the horizontal drive circuit 290, which supplies a current for driving the horizontal output circuit 270,
0 supplies a sufficient deflection current, and the horizontal deflection yoke H-DY synchronizes the video signal displayed on the monitor 200.

On the other hand, the horizontal size signal H-SIZE output from the microcomputer 210 is input to the horizontal size control unit 220, and the horizontal size control unit 220 outputs the horizontal size signal H-SIZE.
SIZE is processed to output a horizontal size adjustment signal. The horizontal size drive circuit 230 amplifies the input horizontal size adjustment signal and outputs it to the horizontal regulation control unit 240.

[0008] The fluctuation of the sawtooth current output from the horizontal output circuit 270 is detected by the regulation sensor 240. The regulation sensor 240 that has sensed the fluctuation of the sawtooth current outputs the sawtooth current fluctuation signal corresponding to the magnitude of the fluctuation to the horizontal regulation control unit 25.
Output to 0.

A horizontal regulation controller 250 to which the sawtooth current fluctuation signal and the horizontal size adjustment signal are input.
Outputs a control signal corresponding to the sawtooth current fluctuation signal. The control signal is input to the horizontal regulation output circuit 260. The horizontal regulation output circuit 260 outputs a pulse corresponding to the control signal to the horizontal output circuit 270 to stabilize the sawtooth current output from the horizontal output circuit 270. By stabilizing the saw-tooth wave current output from the horizontal output circuit 270 as described above, the size of the horizontal image displayed on the monitor screen is integrally maintained.

[0010]

Such a conventional duty changing circuit uses a circuit composed of a complicated PWM IC and its peripheral circuits, and has a problem that the circuit configuration becomes complicated.

Therefore, the present invention has been devised to solve the above-mentioned problems, and its object is to
An object of the present invention is to provide a new and improved duty change circuit having a simple circuit configuration using a Schmitt circuit for changing a duty.

Another object of the present invention is to provide a new and improved horizontal duty changing circuit for a display device having a simple circuit configuration.

[0013]

In order to achieve the above object, the present invention provides a duty changing circuit for outputting a horizontal size adjustment signal to a horizontal size drive circuit of a monitor. And a predetermined triangular wave are inputted, the amplifying circuit amplifies the triangular wave at an amplification factor according to the waveform amplifying ratio control signal, and outputs an amplified triangular wave. A duty changing circuit is configured to include a Schmitt circuit that outputs a rectangular wave that is input and that has been duty-converted in accordance with a preset high level and low level as a horizontal size adjustment signal.

Preferably, the duty changing circuit further includes a DC level adjusting circuit which receives the waveform amplification factor control signal, converts the input waveform amplification factor control signal into a corresponding DC level, and outputs the DC level to the amplification circuit. Including.

Preferably, the duty changing circuit receives a predetermined rectangular wave or a flyback pulse generated in the monitor and generates the predetermined triangular wave according to the input predetermined rectangular wave or flyback pulse. And an integrating circuit for outputting to the amplifying circuit. The integrating circuit may be an RC integrating circuit including a capacitor and a resistor that generate a triangular wave according to an RC time constant.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an internal circuit of a monitor to which an embodiment of a duty changing circuit according to the present invention is applied. As shown in the figure, a monitor 20 outputs a horizontal synchronization signal H-SYNC and a vertical synchronization signal V to synchronize the processed video signal from a video card 11 which performs video signal processing on data processed in the computer main body 10. -SYNC is input.

The monitor 20 outputs a horizontal synchronizing signal H-SYNC and a vertical synchronizing signal V-
A microcomputer 21 that determines a video mode by SYNC and outputs a waveform amplification rate control signal corresponding to a horizontal size adjustment signal based on the determination result, and a horizontal synchronization signal H-SYNC and a vertical synchronization signal V-SYNC output from the microcomputer 21 The horizontal and vertical oscillating signals are input, and the horizontal and vertical oscillating signal processors 22 for compensating the band by inputting the horizontal and vertical oscillating signals and correcting the linearity. A horizontal drive circuit 23 that supplies a large current, a horizontal output circuit 24 that is driven by inputting a sufficient current from the horizontal drive circuit 23 and outputs a sawtooth current, and a horizontal size adjustment signal output from the microcomputer 21 A duty ratio changing circuit unit 25 that receives the input waveform amplification factor control signal and outputs a square wave whose duty has been changed. A horizontal size drive circuit 26 for amplifying and outputting the duty-changed rectangular wave output from the waveform change circuit unit 25, and a saw-tooth wave current change signal which senses a change in the saw-tooth current output from the horizontal output circuit 24. A regulation sensor 27 for outputting, a sawtooth current variation signal from the regulation sensor 27, a horizontal drive signal from a horizontal size drive circuit 26, and a horizontal regulation control unit 28 for stabilizing the output waveform of the sawtooth current; A horizontal regulation output circuit 29, which receives a horizontal size adjustment signal from the horizontal regulation control unit 28 to control the output of the horizontal output circuit 24, and a sawtooth current output from the horizontal output circuit 24, inputs the video signal from the video card 11. Horizontal deflection yoke for synchronizing video signals Mainly composed of the -DY.

In the above-described configuration, the duty changing circuit unit 25 receives the waveform amplification factor control signal corresponding to the horizontal size adjustment signal created by the microcomputer 21 and converts it into a direct current (DC). And a rectangular wave or a flyback pulse generated in the monitor 20 are input, the charge / discharge is performed by the rectangular wave or the flyback pulse, and an integrating circuit 25b that generates and outputs a triangular wave
An amplification circuit 25c that amplifies and outputs a triangular wave input from the integration circuit 25b in accordance with the waveform amplification rate control signal input from the DC level adjustment circuit 25a;
A Schmitt circuit that sets a high level and a low level around a reference level according to the triangular wave input from c, performs duty conversion according to the set high level and low level, and outputs a duty-converted rectangular wave. 25d
It is mainly composed of

Hereinafter, the operation of the duty changing circuit configured as described above will be described. Computer body 1
0 indicates that the data from the program execution is
To convert the data into video data. Video card 11
Outputs a processed video data, that is, a horizontal synchronization signal H-SYNC and a vertical synchronization signal V-SYNC for synchronizing the video signal. The horizontal synchronizing signal H-SYNC and the vertical synchronizing signal V-SYNC are input to a microcomputer 21 built in the monitor 20.

The microcomputer 21 has a horizontal synchronizing signal H-SYN.
When C and the vertical synchronization signal V-SYNC are input, the input horizontal synchronization signal H-SYNC and vertical synchronization signal V-SYNC are input.
The video mode and the polarity are determined according to the SYNC. The microcomputer 21 that has determined the video mode creates and outputs a waveform amplification rate control signal corresponding to the horizontal size adjustment signal corresponding to the determined result. That is, pulse width modulation (PWM)
And outputs the adjusted level signal.

The microcomputer 21 outputs the horizontal synchronization signal H-SYNC and the vertical synchronization signal V-SYNC input from the video card 11 to the horizontal and vertical oscillation signal processors 22. Horizontal synchronization signal H-SYNC and vertical synchronization signal V
Horizontal and vertical oscillation signal processor 2 to which SYNC is input
2 corrects the band according to the horizontal oscillation signal and the vertical oscillation signal to correct the linearity.

The horizontal oscillation signal among the signals processed by the horizontal and vertical oscillation signal processors 22 is input to a horizontal drive circuit 23. The horizontal drive circuit 23 supplies a current for driving the horizontal output circuit 24, and the supplied horizontal output circuit 24 generates a sawtooth wave. At this time,
When an overload occurs in the horizontal output circuit 24 that generates a sawtooth wave, the generated overload is transmitted to the regulation sensor 27.
Is sensed by

On the other hand, a waveform amplification rate control signal corresponding to the horizontal size adjustment signal output from the microcomputer 21 is input to a DC level adjustment circuit 25a in the duty change circuit 25. The waveform amplification rate control signal is input after being converted into a triangular wave of an analog level signal via a D / A converter (not shown). The triangular wave is converted into a direct current (DC) by a DC level adjusting circuit 25a, and the amplified circuit 25c
Is amplified. An integrating circuit 25b to which a rectangular wave or a flyback pulse generated in the monitor is input.
Converts a square wave or flyback pulse to a triangular wave. The triangular wave converted by the integration circuit 25b is amplified and output by the amplification circuit 25c. The triangular wave amplified by the amplifier circuit 25c is duty-converted through the Schmitt circuit 25d. That is, the Schmitt circuit 25d sets a high level and a low level based on the reference level, and performs a duty conversion according to the set high level and low level to output a rectangular wave.

The rectangular wave whose duty has been changed is output to the horizontal size drive circuit 26. The horizontal size drive circuit 26 to which the rectangular wave whose duty has been changed is input sufficiently amplifies and outputs the rectangular wave.

The rectangular wave from the horizontal size drive circuit 26 and the overload detection signal from the regulation sensor 27 are input to a horizontal regulation controller 28, respectively. The horizontal regulation control unit 28 outputs a compensation signal to the horizontal output circuit 24 via the horizontal regulation output circuit 29 according to the input rectangular wave and the overload detection signal. Horizontal output circuit 2 to which the compensation signal is input
4 corrects the generated overload state and outputs a stable sawtooth current to the horizontal deflection yoke H-DY. The horizontal deflection yoke H-DY synchronizes the video signal.

The above-described duty changing circuit 25 will be described in more detail with reference to FIG. FIG. 2 is a detailed circuit diagram of the duty changing circuit shown in FIG.

As shown in the figure, the microcomputer 21 receives the horizontal synchronization signal and the vertical synchronization signal output from the video card 11 (see FIG. 2), determines the video mode, and converts the video mode into a horizontal size adjustment signal according to the determination result. A corresponding waveform amplification factor control signal is created and output. The waveform amplification rate control signal includes resistors R2 and R3 and a resistor R1 for dividing the waveform amplification rate control signal.
DC level adjusting circuit 25 which is a voltage dividing circuit composed of
a and is converted to DC.

An integrating circuit 25b which receives a rectangular wave or a flyback pulse generated in the monitor and generates and outputs a triangular wave by charging / discharging the input rectangular wave or flyback pulse is supplied to the integrating circuit 25b. Alternatively, it is an RC integrating circuit including a capacitor C and a resistor R4 that receive a flyback pulse and generate a triangular wave according to the RC time constant.

The amplification circuit 25c amplifies the triangular wave according to the waveform amplification rate control signal input from the integration circuit 25b and outputs the result. The amplifier circuit 25c includes a transistor Q1 for amplifying a triangular wave based on the waveform amplification rate control signal, and a plurality of resistors R
5 to R7.

The Schmitt circuit 25d includes an amplifying circuit 25c.
A high level and a low level are set around a reference level in accordance with the triangular wave output from the CPU, duty conversion is performed in accordance with the set high level and low level, and a duty-converted rectangular wave is output. The Schmitt circuit 25d includes transistors Q2, Q3, Q4, and a plurality of resistors R8 to R1.
3 and a Zener diode ZD.

The duty changing circuit thus configured operates as follows. The waveform amplification rate control signal, which is a pulse width modulation (PWM) level signal output from the microcomputer 21, is input to a DC level adjustment circuit 25 c in the duty change circuit 25. DC level adjustment circuit 25a
, A waveform amplification factor control signal is input through a resistor R1, and a reference voltage Vref applied through resistors R2 and R3.
The voltage is appropriately divided in accordance with and converted to DC. The DC level is adjusted according to the reference voltage Vref and the resistance values of the resistors R2 and R3.

The waveform amplification factor control signal whose DC level has been adjusted is input to the base of the transistor Q1 of the amplifier circuit 25c. The transistor Q1 outputs a triangular wave obtained by amplifying the triangular wave input to the collector according to the waveform amplification factor control signal.

As shown in FIG. 3, the integration circuit 25b generates a triangular wave using a rectangular wave or a flyback pulse generated in the monitor. The integration circuit 25b outputs the input rectangular wave or flyback pulse as a triangular wave according to the time constant RC of the resistor R4 and the capacitor C.

The triangular wave is passed through the resistor R5 to the amplifier circuit 25c.
Of the transistor Q1. The triangular wave input to the collector is amplified according to the waveform amplification rate control signal input to the base of the transistor Q1. The amplified triangular wave passes through a resistor R7 and a Schmitt circuit 25d.
Is output to

In the Schmitt circuit 25d, the triangular wave is input to the base of the transistor Q2. A drive voltage (+12 V) is applied to the emitters of the transistors Q2 and Q3 through a resistor R8. Transistors Q2, each having a drive voltage (+ 12V) applied to the emitter,
Q3 is turned on / off at the time of rising and falling of the input triangular wave, and changes the duty according to the high level and the low level preset for each element value. Output signals output from the transistors Q2 and Q3 are input to the base of the transistor Q4 via the resistor R13. A drive voltage (+12 V) is applied to the collector of the transistor Q4 to drive. Transistor Q
2, a transistor Q4 to which an output signal from Q3 is input.
Outputs an amplified rectangular wave according to the input signal. To stabilize the output of the square wave, the transistor Q
A feedback loop via a resistor R12 is provided between the collector of the transistor 4 and the base of the transistor Q3. The rectangular wave fed back via the resistor R12 is appropriately divided by the resistors R10 and R11 and input to the base of the transistor Q3. By providing this feedback loop, the output of the duty-changed rectangular wave output from the transistor Q4 is stabilized. The resistor R9 is the collector resistor of the transistor Q3, and the Zener diode ZD keeps the output of the output rectangular wave constant.

FIG. 3 is a waveform diagram showing the waveform at the output point of each circuit constituting the duty changing circuit shown in FIG.
As shown, the waveform a is a waveform generated from the output point 'a' and is a waveform of a waveform amplification rate control signal corresponding to the horizontal size signal adjustment signal. The waveform b is a waveform generated from the output point 'b', and converts a rectangular wave and a flyback pulse generated in the monitor into a triangular wave by the integration circuit 25b according to the waveform amplification rate control signal output from the microcomputer 21. This is the waveform obtained. Here, the waveform b1 and the waveform b2 are waveforms corresponding to the potential level difference. The duty width of the pulse generated by the Schmitt circuit 25d is changed based on the waveform b. That is, according to the waveform b1, the Schmitt circuit 25d
Is a waveform in which the pulse width of the pulse in the waveform c is 'c1'. Further, the output waveform becomes a waveform having a pulse width of 'c2' in the waveform c due to the low level and high level points of the waveform b2. Thus, the duty width can be changed according to the waveform rate amplification control signal through the Schmitt circuit 25d.

Although the preferred embodiment of the duty changing circuit according to the present invention has been described with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such an example. It is clear that a person skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and those modifications naturally fall within the technical scope of the present invention. It is understood to belong.

[0039]

As described above, according to the duty changing circuit according to the present invention, the duty of the pulse input to the horizontal size drive circuit of the monitor is changed with a simple configuration, and the distortion of the monitor screen due to the high voltage fluctuation is reduced. Can be corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of an internal circuit of a monitor to which an embodiment of a duty changing circuit according to the present invention is applied.

FIG. 2 is a detailed circuit diagram of a duty changing circuit of FIG. 1;

FIG. 3 is a waveform diagram showing a waveform at an output point of each circuit shown in FIG. 2;

FIG. 4 is a block diagram showing a configuration of a conventional duty control circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Video card 21 Microcomputer 22 Horizontal and vertical oscillation signal processor 23 Horizontal drive circuit 24 Horizontal output circuit 25 Duty change circuit 25a DC level adjustment circuit 25b Integration circuit 25c Amplification circuit 25d Schmitt circuit 26 Horizontal size drive circuit 27 Regulation sensor 28 Horizontal regulation Control unit 29 Horizontal regulation output circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G09G 1/16 G09G 1/00 G09G 1/04 H04N 3/223 H03K 5/04

Claims (4)

(57) [Claims] A duty changing circuit for outputting a horizontal size adjustment signal to a horizontal size drive circuit of a monitor receives a waveform amplification factor control signal from a microcomputer and a predetermined triangular wave, and responds to the waveform amplification factor control signal. An amplifying circuit that amplifies the triangular wave at an amplification factor and outputs the amplified triangular wave; and a rectangular wave to which the amplified triangular wave is input and subjected to duty conversion according to a preset high level and low level, and And a Schmitt circuit for outputting as a size adjustment signal.
Duty change circuit. 2. The apparatus according to claim 1, further comprising a DC level adjustment circuit to which the waveform amplification rate control signal is input, converts the input waveform amplification rate control signal into a corresponding DC level, and outputs the DC level to the amplification circuit. The duty changing circuit according to claim 1, wherein 3. A predetermined rectangular wave or a flyback pulse generated in the monitor is input, and the predetermined triangular wave is generated in accordance with the input predetermined rectangular wave or flyback pulse, and is output to the amplifier circuit. The duty changing circuit according to claim 1, further comprising an integrating circuit for outputting. 4. The duty changing circuit according to claim 3, wherein said integration circuit is an RC integration circuit comprising a capacitor and a resistor for generating a triangular wave according to an RC time constant.